Fix: libcurl HTTP thread race at uninit preventing thread exit

src/network/core/http_curl.cpp

@@ -230,8 +230,10 @@ void HttpThread()
 			request->callback.OnFailure();
 		}
 
-		/* Wait till the callback tells us all data is dequeued. */
+		/* Wait till the callback tells us all data is dequeued, or _http_thread_exit has been set. */
-		request->callback.WaitTillEmpty();
+		request->callback.WaitTillEmptyOrCondition([]() -> bool {
+			return _http_thread_exit;
+		});
 	}
 
 	curl_easy_cleanup(curl);
@@ -278,6 +280,11 @@ void NetworkHTTPUninitialize()
 
 	_http_thread_exit = true;
 
+	/* Queues must be cleared (and the queue CV signalled) after _http_thread_exit is set to ensure that the HTTP thread can exit */
+	for (auto &callback : _http_callbacks) {
+		callback->ClearQueue();
+	}
+
 	{
 		std::lock_guard<std::mutex> lock(_http_mutex);
 		_http_cv.notify_one();

src/network/core/http_shared.h

@@ -75,13 +75,15 @@ public:
 	}
 
 	/**
-	 * Wait till the queue is dequeued.
+	 * Wait till the queue is dequeued, or a condition is met.
+	 * @param condition Condition functor.
 	 */
-	void WaitTillEmpty()
+	template <typename T>
+	void WaitTillEmptyOrCondition(T condition)
 	{
 		std::unique_lock<std::mutex> lock(this->mutex);
 
-		while (!queue.empty()) {
+		while (!(queue.empty() || condition())) {
 			this->queue_cv.wait(lock);
 		}
 	}
@@ -95,6 +97,20 @@ public:
 		return this->queue.empty();
 	}
 
+
+	/**
+	 * Clear everything in the queue.
+	 *
+	 * Should be called from the Game Thread.
+	 */
+	void ClearQueue()
+	{
+		std::lock_guard<std::mutex> lock(this->mutex);
+
+		this->queue.clear();
+		this->queue_cv.notify_all();
+	}
+
 	HTTPThreadSafeCallback(HTTPCallback *callback) : callback(callback) {}
 
 	~HTTPThreadSafeCallback()